1. Technical Field
The embodiments of the present invention described herein generally relate to a system for hydrogen recirculation using integrated motor/generator energy.
2. Background Art
It is generally well known that a number of fuel cells are joined together to form a fuel cell stack. Such a stack generally provides electrical current in response to electrochemically converting hydrogen and oxygen into water and energy. The electrical current is used to provide power for various electrical devices in the vehicle. A supply (or fuel tank) generally provides hydrogen to the fuel cell stack. The fuel cell stack may use less hydrogen than provided by the supply to generate electrical power. The excess or unused hydrogen is discharged from the fuel cell stack and recirculated with the supply hydrogen and sent back to the fuel cell stack. A blower/compressor may be used to combine the unused hydrogen discharged from the fuel cell stack with the supply hydrogen to sustain a desired flow of hydrogen to the fuel cell stack. The recirculation of such unused hydrogen may improve fuel efficiency and stability.
The amount of flow of hydrogen that is passed through the fuel cell stack and needed to produce electrical current fluctuates based on vehicle level power consumption and vehicle operating attributes. In a high power consumption mode, the flow of the hydrogen through the fuel cell stack is generally high since the fuel cell stack has to consume more hydrogen at a relatively faster rate in order to meet higher power demands for the vehicle.
During a low power consumption mode, it may be necessary to increase the flow of the hydrogen through the fuel cell stack since the fuel cell stack consumes and discharges unused hydrogen at a relatively slower flow rate. Such a slow flow rate of hydrogen may affect the life span of the fuel cell stack and affect the production of electrical power thereby leading to operational inefficiencies.
While the blower/compressor is particularly useful for recirculating unused hydrogen back to the fuel cell during low and high power consumption modes in order to meet desired hydrogen flow rates, the blower/compressor generally consumes a large amount of power from the power supply of the vehicle to operate. Particularly, in the low power consumption mode since the blower/compressor has to increase the flow of the unused hydrogen back to the fuel cell stack to compensate for the reduced flow of unused hydrogen discharged from the fuel cell stack.
Accordingly, it would be useful to provide an alternative power source which produces electrical or mechanical power that may be used to drive the blower/compressor in order to minimize power consumption during various fuel cell stack operational modes. In addition, it would be useful to store excess power generated by the alternative power source in moments where the blower/compressor operates in a limited capacity or in no capacity at all so that other power consuming devices in the vehicle may consume the stored excess power.